Infant leg twitching and trembling may be caused by underdeveloped brain, calcium or vitamin D deficiency. 1. The brain is not yet well developed: Since the brain of infants is not yet well developed, certain movements of infants are affected by the generalization of nerve conduction, so they show unconscious trembling, which is a normal phenomenon. 2. lack of calcium or vitamin D: vitamin D can promote calcium absorption, when the baby lacks calcium or vitamin D, there will be a phenomenon of leg twitching and trembling, timely calcium can be relieved. When infants have leg twitching and trembling, it is recommended to go to the hospital for a comprehensive examination to clarify the cause, and take targeted treatment under the guidance of the doctor.